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Growing Groceries.com

The Ultimate Tool for Measuring Plant Health

Posted: 09 Dec 2008 09:20 PM CST

I should preface this post with the disclaimer “Serious and Geeky Gardeners Only” as only the most obsessed among us would desire such a garden tool as this. It ain’t yo’ mama’s three prong cultivator.

A refractometer is very likely the best instrument available to measure the health of your plants. Refractometers are used in a multitude of fields ranging from medical to scientific, to beekeeping. They are most often used to measure the dissolved solids (sucrose, for instance) in a liquid substance- the Brix reading. On the surface this seems like it would have no application whatsoever to gardening, but it can be quite a powerful tool to let you know just what’s going on with your plant. It can also give you clues into the nutritional value of your produce.

For gardeners, in the simplest of terms, a refractometer will tell you if your plant has watery cells. Watery cells are bad. Bad watery cells! You want your plants to have lots of dissolved solids like sugar. A high Brix reading means your plant has a higher carbohydrate level than a plant with a low Brix reading.

This is helpful in monitoring the health of your garden crop. Think of the Brix scale as a measurement of a plant’s immune system. A plant with a low Brix reading is more susceptible to disease and even insect damage. By monitoring the Brix, you can identify and correct problems before they become problems.

For instance, if you regularly test your tomato plants with a refractometer, you may notice a steadily declining Brix reading. You can takes steps to raise it mid-season, by side-dressing or foliar spraying to bring the Brix back up again before it translates into a serious problem.

It’s also helpful as a guide to measure the progress of your soil’s health and your elite skills as a gardener. If your tomato plants have a Brix reading of 6 and the next year have a reading of 8, you can pat yourself on the back for being so flippin’ cool. On the other hand, if last year your Brix was 9 and this year it’s 7, you will be able to ask yourself “What was I doing then that I’m not doing now?”

Of course, everything has it’s limitations and drawbacks and refractometers definitely have their fair share. In very small gardens, it’s not practical to test very often. Testing is done by squeezing sap from parts of the plant- leaves, stem, etc. If you only have two tomato plants, the amount of plant material you’d need to collect would hurt the plant if done regularly. If you have twenty tomato plants, then it’s much easier to spread the damage around so no one plant is affected from loss of it’s parts. Capesh? You have to have enough plants to take an average sample from.

How to Use a Refractometer in the Garden

A Refractometer is pretty simple to use, depending on your model. I have a traditional portable refractometer I bought from GrowOrganic.com. Digital refractometers are also available for a higher price, but this one works fine. It consists of a prism, a focusing eyepiece, and a plate over the prism that smooths the liquid across the prism. The reading goes up to 32 on the Brix scale, which is plenty for agricultural use.

They can be pricey. I bought mine for around 90 bucks. If you find a source for a similar refractometer at a lower price, please let me know. For me, I think it was worth the investment.

The liquid extracted from the plant is dropped onto the prism and the plate is shut, making sure the liquid covers the entire area of the prism. You then point the plate towards the sun and look through the eyepiece..you’ll see something like this, but with more numbers.

Am I not a great artist?

You then read the number where the two colors meet and that’s your Brix reading! Nothing to it, right? Note it down in you garden journal,clean of the prism off with a soft, damp cloth and your done!

Extracting Sap

The difficult part is actually getting the sap out of the plant. Try as you may using household devices, there’s no substitute for a sap press (expensive) or a modified pair of vice grips like the ones sold at GrowOrganic (not so expensive). Even with these tools it takes practice. Practice with weeds until you get the sap squeezing thing down so you don’t defoliate all the plants in your garden.

* The Brix number in and of itself isn’t as important as how it compares to the previous number. Although there are guides as to what Brix level is good for such and such a veggie, many different variables can change the Brix. Such as the area of the plant the reading was taken from.
* Be Consistent! Make sure you take from the same plant parts each time or you may get wildly different readings. If you take a sample from the lower leaves, always take a sample from the lower leaves. If you take a sample from stems near the top, always take them there.
* It’s helpful to graph out your results. It’s also fun. Take your seasonal or multi year data and graph your improvement over time. You’ll also start to make connections on what causes jumps in Brix readings.
* Be sure to follow all the calibration instructions that come with your refractometer before using it!

I encourage you to give this thing a try if you have a little extra Christmas cash laying around. Or perhaps give one as a Christmas gift to a beloved gardener!
GrowingGroceries.com

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